排序方式: 共有73条查询结果,搜索用时 373 毫秒
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M. Lampe 《Journal of Geometry and Physics》2012,62(3):646-656
The conformal isotropy algebra of a point m in an n-manifold with a metric of arbitrary signature is shown to be locally reducible, by a conformal change of the metric, to a homothetic algebra near m iff, by choice of a chart, its constituent vector fields are simultaneously linearisable at m and, for n≥3, a necessary and sufficient condition for this in terms of the first and second derivatives of these fields at m is given. The implications for the Riemannian case and the Lorentzian case are investigated. In contrast to the former, a Lorentzian manifold admitting a conformal vector field that is not linearisable at some point need not be conformally flat. Relevant four-dimensional examples are provided. 相似文献
23.
We give a precise expression for the universal weight function of the quantum affine algebra U
q
(
). The calculations use the technique of projecting products of Drinfeld currents on the intersections of Borel subalgebras.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 145, No. 1, pp. 3–34, October, 2005. 相似文献
24.
Let
be a central simple Lie algebra over a field
. We study the maximal ℤn-graded subalgebra of
.
Mathematics Subject Classifications (2000) 17B70, 17B65, 17B67. 相似文献
25.
Peter M. Schuster 《Proceedings of the American Mathematical Society》1998,126(7):1983-1987
We construct a space of fine moduli for the substructures of an arbitrary compact complex space . A substructure of is given by a subalgebra of the structure sheaf with the additional feature that is also a complex space; and are called equivalent if and only if and are isomorphic as subalgebras of .
Since substructures are quotients, it is only natural to start with the fine moduli space of all complex-analytic quotients of . In order to obtain a representable moduli functor of substructures, we are forced to concentrate on families of quotients which satisfy some flatness condition for relative differential modules of higher order. Considering the corresponding flatification of , we realize that its open subset consisting of all substructures turns out to be a complex space which has the required universal property.
26.
Recently F. Huang [Commun. Theor. Phys. 42 (2004) 903] and X. Tang and P.K. Shukla [Commun. Theor. Phys. 49 (2008) 229] investigated symmetry properties of the barotropic potential vorticity equation without forcing anddissipation on the beta-plane. This equation is governed by two dimensionless parameters, F and β, representing the ratio of the characteristic length scale to the Rossby radius of deformation and the variation of earth' angular rotation, respectively. In the present paper it is shown that in the case F≠ 0 there exists a well-defined point transformation to set β= 0. Theclassification of one- and two-dimensional Lie subalgebras of the Lie symmetry algebra of the potential vorticity equation is given for the parameter combination F≠0 and β = 0. Based upon this classification, distinct classes of group-invariant solutions are obtained and extended to the case β≠ 0. 相似文献
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28.
It is proved that over every countable field K there is a nil algebra R such that the algebra obtained from R by extending the field K contains noncommutative free subalgebras of arbitrarily high rank.It is also shown that over every countable field K there is an algebra R without noncommutative free subalgebras of rank two such that the algebra obtained from R by extending the field K contains a noncommutative free subalgebra of rank two. This answers a question of Makar-Limanov [Lenny Makar-Limanov, private communication, Beijing, June 2007]. 相似文献
29.
M. Ceballos 《Applied Mathematics Letters》2012,25(3):514-519
This work shows how to associate the Lie algebra hn, of upper triangular matrices, with a specific combinatorial structure of dimension 2, for n∈N. The properties of this structure are analyzed and characterized. Additionally, the results obtained here are applied to obtain faithful representations of solvable Lie algebras. 相似文献
30.
We study the weak hereditary class S
w
(
) of all weak subalgebras of algebras in a total variety
}. We establish an algebraic characterization, in the sense of Birkhoff’s HSP theorem, and a syntactical characterization
of these classes. We also consider the problem of when such a weak hereditary class is weak equational. 相似文献